How to tell if your switchboard is single phase or three phase?

Find out if your switchboard is single phase or 3 phase and how that affects your solar system

One of the key questions you need to answer while deciding on going with solar power is - whether the grid power supply to your house is single phase or three phase. A single phase grid supply will need a single phase solar inverter. However, a three phase grid supply can work with both single phase and three phase solar inverters. This article helps you identify if your household receives single phase or three phase grid power supply. 

Electricity is generated in power plants and transmitted through an electricity network consisting of sub stations, step-up and step-down transformers and power lines to reach the households. Household electricity supply can be broadly classified into single phase power supply and three phase power supply. Most households in Australia receive single phase power supply. Larger households receive three phase power supply.

The easiest way to identify if you receive a single or three phase power supply is to look at the main breaker within your switchboard. If the main breaker has a single-pole breaker, your household receives a single phase power supply. If the main breaker has a three-pole breaker your household receives three-phase power supply.

Single phase power supply lets you operate electrical equipment that are compatible with 230 V AC power and three phase power supply lets you operate electrical equipment that are compatible with 230 V AC power and 415 V AC power.

The below diagram explains the different steps between power generation and consumption. 

Figure 1: U.S. Energy Information Administration

What is single phase power?

In single phase power, the AC power takes the shape of a sinusoidal wave, the voltage in a single phase supply peaks at 900 during the positive cycle and again 2700 during the negative cycle. The phase wire carries the current to the load and the neutral wire provides the return path of the current. Single phase voltage is usually 230 V and the frequency is 50 Hz. Since the voltage in a single phase supply rises and falls, a constant power cannot be delivered to the load. 

Figure 2: https://www.electronicshub.org/difference-between-single-phase-and-three-phase/

Single phase power is a two-wire alternating current power circuit. There is one power wire, also called the phase wire, and one neutral wire. Most residential households are served by a single-phase power supply. 

What appliances can I run-in single-phase power?

Most common household items including lights, fans, laptops, computers, television sets, fridges, cooking range, heaters and air conditioners are single phase. Larger loads like industrial motors cannot be run on a single-phase supply as there isn’t sufficient torque for the motor to start. It’s important to note you cannot run an equipment that requires three phase power supply with single phase power.

How can I verify my house receives single phase power?

There are two easy ways to identify if your household receives single phase power or not. The first, the easier way, is to locate your energy meter and read the description on the meter. 

Figure 3: https://www.indiamart.com/proddetail/static-single-phase-two-wire-energy-meter20462826530.html

In the above picture, it can be observed that on the meter the description is very clear “Static Single Phase Two Wire Energy Meter”.

The next best way is to locate your main switch board and count the number of poles on the main breaker. You can locate your main switch board next to the energy meter. If the main breaker has one pole, then the power supply to your household is single phase. Below is a picture of a 63 A single pole breaker. 

Figure 4: https://connectedswitchgear.com.au/our-range/fusion-series-circuit-protection/mcbs/10ka/1-pole-10ka/circuit-protection-mcbs-10ka-1-pole-d-curve/mcb1106d/

What is three phase power?

In three phase power supply, during one cycle of 360o, each phase would have peaked in voltage twice and the power never drops to zero. This steady stream of power and ability to handle higher loads makes a three-phase supply suitable for large industrial and commercial loads. 


Figure 5: https://www.electronicshub.org/difference-between-single-phase-and-three-phase/

Three phase power is a four-wire alternating current power circuit. There are three power wires, also called the phase wire, and one neutral wire. Current flows through the power wire, through the load and returns through the neutral to complete the circuit. Commercial and industrial facilities and large residential households are usually served by three phase power supply. Three phase power supply can support both single phase and three phase appliances.

What appliances can run on three phase power?

Large air conditioners, saunas, pool heaters, electric car chargers, refrigeration units, deep freezers are common three phase equipment found in households. 

How can I verify my house receives three phase power?

The first step is to locate your energy meter and read the description written on the meter. On the below meter its is written, “3 Phase 4 Wire Energy Meter”. This is perhaps the easiest way to identify if your house hold receives three phase or single phase power supply. 


Figure 6: https://www.lntebg.in/products-services/products/meters/bidirectional-net-meters/three-phase-ltct-meter-er300p/

The alternative is to locate your main switch board and count the number of poles on the main breaker. You can locate your main switch board next to the energy meter. If the main breaker has three poles, then the power supply to your household is three phase. Below is a picture of a 80 A three pole breaker. 

Figure 7: https://connectedswitchgear.com.au/our-range/fusion-series-circuit-protection/main-switches/ms380/

What does this mean when planning a solar panel installation?

All households run on AC power (alternating current), the first step is to understand that the power produced from solar panels is DC power (direct current). A solar inverter is needed to convert the DC power produced by the solar panels into AC power. The solar inverter is available in two different power classes. First is single phase power and the second is three phase power. 


Figure 8: https://www.siliconsolar.com/on-grid-vs-off-grid/

If the power supply from the grid to your household is single phase, you are restricted to only use a single phase solar inverter. However, if the power supply to your household from the grid is three phase, you can chose to either use a single phase or a three phase solar inverter. 

Single phase vs 3 Phase solar inverter?

A single phase inverter has 2 cables. One live cable and one neutral cable. A three phase inverter has 4 cables, three live cables and one neutral cable. A three phase inverter sends solar electricity uniformly across the three phases which minimises phase imbalance. 

For solar systems upto 5 kWp size, a single phase inverter is recommended. There are rarely three phase solar inverters from reputable suppliers for system sizes less than 5 kWp. Larger solar installations will need three phase solar inverters. 

If you have a 3 phase switchboard, should you get a 3 phase solar inverter? Or stick with a single phase inverter?

There are significant benefits in using a 3 phase solar inverter, especially if you are considering a solar installation greater than 5 kWp. However 3 phase inverters are also expensive when compared to single phase. 

The easiest way to answer this question is - if the solar system you are planning to install is greater than 5 kWp or if there is a probability that you start with a smaller solar plant and scale it to a larger roof top solar system in future, it's worth considering a 3 phase solar inverter, else its better to use a single phase solar inverter. 

Adding batteries in your solar plant will have no effect on the decision making process of choosing a single phase or three phase solar inverter. 

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